The present invention relates generally to an instrument interconnect cable, and more particularly to an instrument interconnect cable wherein the user can adjust the cable's capacitance.
Guitars and other stringed instruments are often amplified by attaching a passive magnetic pickup in close proximity to the vibrating metallic strings of the guitar and connecting this pickup to an amplifier and speaker using a cable. The vibrating strings change the magnetic flux within the core of the pickup. This flux change induces a voltage change in the outer coils of the pickup, thus completing the translation of mechanical vibration to electrical signal. This signal is transmitted through the cable to the amplifier.
The cable connecting the pickup to the amplifier is typically between 5 and 30 feet to allow the musician adequate mobility while playing. The cable typically is terminated on each end with a standard ¼′ male connector. Both the guitar and amplifier will typically have the mating female ¼″ connector.
Instrument cables are typically of the coaxial type, wherein the signal is surrounded by a 360-degree metallic wire shield. This type of cable protects the very low voltage signal coming from the instrument from radio frequency interference (RFI) or electro-magnetic fields (EMF).
Some musicians have noticed that different brands of instrument cables at different lengths will cause a difference in tonality in an instrument's sound output. One cause for this variance in tonality is the variance in the overall capacitance of the cables being used. Capacitance in cables is caused by the insulating material having a dielectric quality that causes capacitive coupling between the signal wires and the ground, or shield, wires. Coaxial cables are typically given a capacitance per foot rating (pF/ft). This rating typically can be anywhere from 10 pF/ft to 50 pF/ft. By multiplying the pF/ft rating by the length of the cable, a person can calculate the overall capacitance of a particular length of a particular cable. The overall capacitance of a cable typically ranges from 300 pF to 1200 pF. Cables of different capacitances will have different tonal qualities when used with an instrument having passive magnetic pickups.
With present cables, musicians are able to vary the capacitance only by using different cables of different lengths. This is inconvenient for several reasons. First, if a musician wants to produce the same tonality from his or her instrument, then he or she must use the same cable with the same length all the time, or the musician must try to find two or three cables of different lengths that have the same capacitance, exchanging one for the other whenever a cable of a different length is needed. Additionally, if a musician would like to take advantage of the different tonalities offered by cables having different capacitances, then he or she must undertake the inconvenient process of unplugging one cable and then plugging in another having a different capacitance to replace it. The current options available for addressing this issue do not offer a sufficient range of adjustment for altering the capacitance.
It can readily be appreciated that there is a need for an instrument cable that avoids the problems described above. The present invention fulfills this need and provides further related advantages.